Mastertemp overheating issue

[MartinG]

Hello all,

I'll try to make this brief as it's been a strange six week ordeal with my heater, but after 4 tech visits and a lot of "opinions", I am beginning the question the help I'm getting. I may say a few things incorrectly as I am still learning how heaters work and the proper terms.

Pool specs: 10,000 gallon AGP, Backyard Systems/Waterway II filter/pump system (2-speed), less than 4 feet of water piping between every component.

Issue: Six month old Mastertemp 125 hits hit temp (SFS) limit (480 degrees) and shuts down within 10 minutes. No error codes - just service heater light.

History: Ran fine last season but we only had about six weeks of operation as the pool wasn't done until August (I live in Ohio). Fired it up mid-April and started to see the issues. I called my pool installer first and a heater guy came out, opened up the manifold and saw calcium deposits. He "chemically cleaned" the heater, closed it up and called it a day. Issue recurred. Same guy came back, cleaned it again (more deposits/pieces had broken loose and were sitting in the manifold). Issue recurred. I called Pentair, who had a warrantied support guy come out. This guy checked to make sure the SFS was working and he said it was fine. He checked the gas flow, said water column was within spec. He took the unit apart, saw sooting in the heat exchanger and some of the fins were clogged up (I saw this, forgot to get a picture).. Anyhow - after all that, the main issue still recurred. I'm waiting on my second warranty visit now.

Some more info: No corrosion issues seen when unit was disassembled. First tech said my water balance was way off (high alkaline) and that caused the deposits. I pulled my test history (I went weekly to have it checked by someone other than me) and this is not the case. pH was 7.8 for about 2-3 days and I corrected it (was 7.4 next reading, within 3 days of the 7.8). Either way, there was never a sustained out of balance time period during the six weeks the pool was in use. Second tech guy said wind could be causing a 'reburn' of exhaust (high winds not allowing the flue to disperse properly. Yes, we live near Lake Erie and do get high winds. The unit is not enclosed in any way, but unless the wind was high every single day (it wasn't), I can't see this happening when the heather ran for 2-3 hours per day in the morning to regain lost temp overnight.

So, it appears there may be two issues, but I can't say that either of them are directly related to the overheating, especially since "both" have been "resolved" and the overheating still occurs. Water flow rate at the high pump speed is very strong. At the low pump speed, it's not and seems weaker than it was last year, however I know you should use the higher speed. Last season, I did NOT do this (I wasn't told anything about this but my flow rate should be 20-100 at any given time). I have replaced the filter, run the system without filter (and without the Frog chlorine pack just to ensure exit flow isn't being restricted). I know this unit has a lot of built-in systems to prevent damage (internal bypass, flame/burn sensors) so I am just baffled how things got bad so quickly.

That's a huge post - I'm just not sure where to go from here. Everyone's busy now since it's pool season in Ohio, which is one reason I opened my pool so early (April) but that hasn't proven to be worth it without a working heater. I'm so frustrated. How can I wreck my heater (if I did) in six weeks. I'll take responsibility for that, but I want to stop this from recurring.

Thanks for any feedback.

 

[mknauss]

Sorry you have had no help === lets give this a bump and see if someone can help out.

 

[Arizonarob]

James any thoughts? @JamesW

 

[JamesW]

What LEDs on the back of the board are coming on?

Do you have a picture of the system?

 

[PTS]

If the heater is tripping out on a SFS code, meaning the exhaust is 480 degrees or above, heat exchange to the water is being hindered and excess heat is being dumped out of the exhaust.
Normally, only three conditions exist that cause this problem.
Calcified exchanger (internal)
Sooted exchanger (external)
High pressure/low flow water through heater (related to calcification of exchanger)

The way to determine whag is happening is by pulling the manifold and having a look at the exchanger tubes directly.
If there is calcium built up, there's your problem. It absolutely is related to chemistry.
If the exchanger is sooted, removing the exchanger and using a nylon bristle brush, clean it. Should be problem solved for a while. Soot is being developed because of a non-stoichiometric air/fuel ratio, leading to a dirty burn - ultimately a gas issue.

 

[MartinG]

Thank you - sorry for the lack of replies. Shortly after my initial post I went out of town for a few days.

I did talk to a Pentair representative today and he basically said the same things concerning two possible causes: calcification (chemical) and a poor burn (low pressure, mixture). I think my issue is/was - there was both! Since both technicians each found a specific thing, it was confusing to me, which issue I had (and if they were related). After talking to the Pentair guy, I believe I may have caused the initial chemical buildup issue by running the pump on the low setting last season. The part that baffles me the most is how quickly the issue recurred, after a new exchanger was installed (within 12 hours). I can't imagine there would be buildup already (with the chemicals in balance) so this tells me it's a gas issue - but again within 12 hours? Cleaned-out manifold, new exchanger, issue recurs, and now if fired up, the unit exceeds 450 degrees within 10 minutes. It just seems crazy..

I'll pull off the manifold to take a look and get a picture to see what the current situation is. If there's buildup in there already, I will be baffled. I will also get a current, accurate chemical test done to get proper numbers, which may help my warranty ticket, or at least narrow down the current issue.

Thanks again

 

[ajw22]

You say your chemicals were in balance. Can you provide the numbers? What test kit do you use?

The Langelier saturation index and its derivative Calcium Saturation Index (CSI) - Trouble Free Pool that TFP uses calculates the potential to scale. We calculate CSI using PoolMath

 

[JamesW]

Do you have any reason to think that there might be very high phosphates or sulfates in the water?

Are you getting any weird crystals or scale anywhere?

When you start the heater, are you watching the stack flue temperature as it climbs?

When the heater starts, press and hold the "On" button until the stack flue temperature is displayed.

Check the thermal regulator.

Try running with the regulator removed.

Do you have a picture of the system?

Does the pump turn off while the heater is still operating?

Do you have an external bypass that's open?

You might have a bad internal bypass that's allowing too much water to bypass the heat exchanger causing the water in the exchanger to get very hot and scale up.

 

[MartinG]

Here is a picture of the system. I will include recent chemical readings as well. Answers below.

I use the test kit that came with the chlorine/chemicals (Frog). They are standard test strips. I also take a water sample up to the pool store where they use a computerized system to read the levels (the data below is from those readings). I do not have an external bypass. The pump does not shut off (there is no automation and the pump has never shut down for any reason aside from me doing so). Initially, one tech did run the heater without the regulator installed. Yes, I have stood there and watched the temp rise. Initially it goes to about 325 and climbs steadily for 10 minutes. Once it gets to 460 or so, I shut it off to prevent things from getting worse. After the exchanger was replaced (work finished around noon), the unit didn't shut off until midnight, 12 hours later. I fired it back up the next morning so I could watch the temp climb, and it only took 10-15 minutes tops (also strange - once it happens after a tech visit, the second time takes much less time to reach max temp).

Edit: more info about the system. I did run the system/heater without the chlor packs and filter a few weeks ago as I suspected a flow issue. No change - overheating still occurs. On high, the water jet out of the return is very strong, so I no longer feel there is restriction. However, there is a check valve at the heater exit pipe (I will check to see if there is anything in there when I disconnect it later). On high, the PSI reading on the filter is about 17-18. On low, it is 5 (but heater is run with it on high). The flexible pipe is about 3' in length between the filter system and heater intake. It's a 2-speed pump and there's a small chart showing the flow rates (although nothing to specify at what speed). The estimated flow rate using that chart (assuming high speed) is somewhere between 90-110 GPM (my estimate). I believe this is within spec according to the heater manual.

Recent water test results (yes I am aware some are slightly below/above - these are the most current I have "professionally"). This test was shortly after I started to crank up the Frog chlorinator system, and right before the heat exchanger replacement (about a week before).

• Free Avail Chlorine: .09 ppm
• Total Chlorine: 1.48 ppm
• Combined Chlorine: 0.56 ppm
• pH: 7.4
• Total Alkalinity: 98 ppm
• Calcium Hardness: 311 ppm
• Cyanuric Acid: 9 ppm
• Copper, Iron: 0 ppm
• Sat Index: .3

I noticed phosphates are not on every reading, but one I have from last year, says 0. I'll have to ask to have this checked next time I take a sample up. It's possible they do not test every time so the printout does not list a value.

I do not have an official gas pressure reading, but I may call Pentair to see if it was recorded from the first tech visit (since he said he measured it).

Thanks all..

 

[JamesW]

What is the filter pressure?

When is the last time that you cleaned the filter?

Do any of the diagnostic LED’s on the back of board (AGS, AFS, SFS, HLS, PS, or
THERMISTOR) come “on” and stay on?

These are the LEDs:

1.....PS (Pressure Switch)
2.....HLS (High Limit Switch)
3.....SFS (Stack Flue Sensor)
4.....AFS (Air Flow Switch)
5.....AGS (Automatic Gas Shutoff).
6.....Service System
7.....Thermistor
8.....Heating
9.....Pool On
10...Spa On
11...Service Heater.

Check the internal bypass. You can see part of it in the hole where the thermal regulator is by removing thermal regulator. Or, you can see the other side of it by looking in the water inlet.

Does the problem still happen with the thermal regulator removed?

Are you getting a strong flow of water from the returns?

What is the model number of the check valve on the heater outlet? Does it say a spring pressure?

 

[MartinG]

Thanks JamesW, I answered some of those in a an edit to my reply above before you asked them. I have not checked the LEDs yet - I am not overly comfortable disassembling the unit in any way, but it is apparent I will need to do this as a part of normal maintenance so I'll have to fire it up and let it fail. A new filter was put it on May 1st and I've cleaned it twice since then (now doing that weekly). Prior to that, I ran the heater without a filter (once pool was clean and ready to use) to see if the flow rate wasn't good enough (it's always seemed to be fine, even with the old filter in). I only did this to see the temperature reading - once I saw it made no difference, I put the new filter in.

 

[ajw22]

I hate to break it to you but test strips and “professional “ pool store testing is unreliable and more often then not inaccurate. We can’t conclude anything from the tests you have.

Going forward I suggest you do your own water testing using the TFP-100 Test Kits or Taylor K-2096C. See Test Kits Compared. Getting the Speedstir Magnetic Stirrer will make testing easier and more accurate.

Use PoolMath to track your testing history and calculate your CSI.

I also suggest you read ABCs of Pool Water Chemistry and consider adopting TFP pool care methods as described in Pool School - Trouble Free Pool

This all will not get your heater running but may prevent future problems.

Post your test results should you get your own test kit and we may have better insight into if your chemistry is causing problems in your heat exchanger.

 

[MartinG]

What is the filter pressure?

When is the last time that you cleaned the filter?

Do any of the diagnostic LED’s on the back of board (AGS, AFS, SFS, HLS, PS, or
THERMISTOR) come “on” and stay on?

These are the LEDs:

1.....PS (Pressure Switch)
2.....HLS (High Limit Switch)
3.....SFS (Stack Flue Sensor)
4.....AFS (Air Flow Switch)
5.....AGS (Automatic Gas Shutoff).
6.....Service System
7.....Thermistor
8.....Heating
9.....Pool On
10...Spa On
11...Service Heater.

Check the internal bypass. You can see part of it in the hole where the thermal regulator is by removing thermal regulator. Or, you can see the other side of it by looking in the water inlet.

Does the problem still happen with the thermal regulator removed?

Are you getting a strong flow of water from the returns?

What is the model number of the check valve on the heater outlet? Does it say a spring pressure?

Check valve is a Lasco “NSFpw”. I can push the valve open fairly easily with a tool.

The LEDs lit are service heater and SFS, somewhat as expected. I have the unit open but can’t get the manifold bolts out yet (need a tool). There are six bolts. From what I can see so far it looks clean. Once I can get this open I can post a picture. I’m not too comfy pulling out the sensor to check the bypass. I’ll have to look on YouTube to see if this is something I can do. I don’t want to leave this in a state where I can’t circulate water.

 

[MartinG]

I hate to break it to you but test strips and “professional “ pool store testing is unreliable and more often then not inaccurate. We can’t conclude anything from the tests you have.

Going forward I suggest you do your own water testing using the TFP-100 Test Kits or Taylor K-2096C. See Test Kits Compared. Getting the Speedstir Magnetic Stirrer will make testing easier and more accurate.

Use PoolMath to track your testing history and calculate your CSI.

I also suggest you read ABCs of Pool Water Chemistry and consider adopting TFP pool care methods as described in Pool School - Trouble Free Pool

This all will not get your heater running but may prevent future problems.

Post your test results should you get your own test kit and we may have better insight into if your chemistry is causing problems in your heat exchanger.

I don’t disagree with your comments amount the tests I do currently. I have read the chemical guides before and have most of the data, except probably what you are looking for. I figured once I was comfortable enough with my knowledge I could do the proper tests myself. I acknowledge that I need to get this potential chemical issue sorted as I feel since buildup was seen upon first inspection.

 

[JamesW]

Don't remove the manifold bolts. You can see the internal bypass by looking in the water inlet or you can remove the thermal regulator and see the round disc part of the internal bypass.

The video that I linked earlier shows how to remove the thermal regulator.

Disconnect the union at the water inlet and remove the thermal regulator. Then, you can push the bypass by compressing the spring and you should see the disc moving in the thermal regulator hole.

If the internal bypass is good, reassemble everything but leave out the thermal regulator and start the heater and watch the stack flue temperature.

Replace the thermal regulator if it's bad.

 

[MartinG]

Don't remove the manifold bolts. You can see the internal bypass by looking in the water inlet or you can remove the thermal regulator and see the round disc part of the internal bypass.

The video that I linked earlier shows how to remove the thermal regulator.

Disconnect the union at the water inlet and remove the thermal regulator. Then, you can push the bypass by compressing the spring and you should see the disc moving in the thermal regulator hole.

If the internal bypass is good, reassemble everything but leave out the thermal regulator and start the heater and watch the stack flue temperature.

Replace the thermal regulator if it's bad.

Here are some pics. The design is of course slightly different vs the 400

Exit, inlet and overall. I do see the spring mechanism inside the inlet just not sure how to get to it. I can push the valve (assuming that’s the bypass) in to the right with minor effort.

 

[JamesW]

It looks ok. I would not try to remove it.

Try running with the thermal regulator out to see what the stack flue temperature shows.

Maybe it's a bad stack flue temperature sensor?

Maybe try a new sensor. 42002-0024S.

There are several ways to access the stack flue sensor. From the top or through a side panel.

 

[MartinG]

I'm going to try to remove the regulator. I fired it up last evening after taking the pics I sent, and it made a strange noise after firing. I've heard it before but it doesn't last and it's not frequent. I decided to try to find out what it could be, and came across this video:

I can't tell where the sound is, and I'm not sure if this video poster's issue was really the regulator, but the sound is almost identical. My main issue right now is that I can't tell how to remove the regulator - looks like I can just pry it out (the videos for the 400 show a much easier way to get at it). I just want to be sure I can get it back in there. Maybe this is where i need to remove the manifold.

 

[JamesW]

I don't see an easy way to access the thermal regulator on this model like on the 400 model.

If you remove the manifold, you should have all new gaskets and a new thermal regulator ready when you reassemble it.

474973 Coil/Tubesheet Sealing O-Ring Kit

474989 Thermal Regulator.

It might be a problem with the thermal regulator, but I would expect a high limit error if the thermal regulator was not opening correctly.

I'm still questioning the stack flue temperature sensor. Maybe the exhaust isn't getting as hot as it's reading.

Since the stack flue temperature sensor is a relatively inexpensive and easy fix, I think that I would try that first.

 

[MartinG]

Yes, I found the sensor on Amazon for $21. I did ask the tech that came out to confirm the actual temp and he supposedly did, but I agree that's an easy fix. For the rest, I think i'd rather that the warranty guy replace all of that since it would be covered by Pentair.

Edit: I assume the regulator could restrict the flow though, yes? I guess it depends what position it is stuck in, if it is. I know the tech did pull it out and show it to me and it has a nice shiny copper look to it so he assumed it was fine.

Thank you